The present invention relates in general to sound pick-up devices, and more particularly to a sound pick-up device mounted on a stringed musical instrument for electronic sound amplification.
While reference herein is made to a bass viol, double bass viol, upright string bass and other musical instruments of the violin family, it is to be understood that the present invention has application in any stringed instrument employing a bridge on which musical strings are disposed.
The double bass viol produces the principal bass sound for many different musical groups. However, such instruments have been known to have inadequate amplitude. Hence, it is common for large orchestras to have as many as eight bassists for tonal balance in the group. Smaller musical groups, such as dance orchestras and jazz combos, use the bass viol for rhythm as well as bass sound. Without electronic sound amplification, the bass sound is often inadequate to be heard in a group. Hence, bassists often employ electronic sound amplification to develop a sufficient bass sound. The devices heretofore employed for sound pick-up in sound amplification systems sacrificed tone quality and character.
Sound pick-up devices heretofore employed in sound amplification systems for musical instruments were the air coupled microphone, the soundboard contact microphone, the electromagnetic string motion detector and the piezo transducer. The air coupled microphone has frequently been placed in the general vicinity of the sound board or sound holes of the instrument. Such arrangements employed very high quality microphones, with the result that sounds in addition to the musical instrument were detected. The soundboard contact microphone frequently used either a crystal or electromagnetic disc type detector that was attached directly to the soundboard of the instrument. There are various small areas of the soundboard of the bass viol of limited size that emit only part of the overall tone of the instrument, which results in inadequate tone quality and character. There were also tendencies to dampen the natural movement of the soundboard and modify the natural tones of the instrument.
The electromagnetic string motion detector required the use of ferrous strings. The detector was generally mounted under the strings at the lower end of the fingerboard. It sometimes included adjustable individual pole pieces designed to detect the lateral motions of the individual strings. Since the strings were set into various nodal patterns as the musician selected various pitch lengths, there was no single location along the sounding length of the instrument that could be considered ideal for detecting all of the harmonics of the strings.
The piezo-electric transducer detectors were of two basic types. One type was secured by wax or cement to the surface of the bridge. Such an arrangement picked up sound waves travelling in the bridge. Thus, the devices of such an arrangement detected sound waves in a limited area and had inadequate tone quality and character. Additionally, such devices were produced with great sensitivity, which resulted in feed back oscillations when too close to the amplifier. The other type was known as the wedge type transducer device. It was wedged or mounted between the legs of the bridge. The wedge type transducer device employed a cylindrical case made up of a piston and cylinder. A ceramic piezo transducer was disposed in the cylinder to be subject to compressions. A threaded screw was provided for adjustment of the compressive force. A silicon latex seal in the cylinder surrounded the piston. The cylinder and piston were of high mass and had a pointed, conical surface. The high mass, restrictive seal and high frequency deflecting cone shaped mounting points had the tendency to limit frequency response. As a consequence thereof, the tone quality was less than desired. Constant tightening was required to reduce rattling. Feed back oscillations were also problem.